Butler struck early, just nine minutes into the Group B encounter, to give his side an early advantage at Clementi Stadium.
Despite twice going ahead in the match, Tampines Rovers were unable to secure all three points as they allowed Warriors FC to come from behind and to snatch the 3-2 win.
Elated to have opened his account with his new club, Butler was still disappointed not to be celebrating a win.
“Very happy to get my first @MightyStags goal last night, shame about the result but focus now on the cup and the league,” Butler tweeted after the match.
Tampines Rovers coach Rafi Ali was equally disappointed his side couldn’t hold on for the victory.
“When you concede goals like that, like schoolboys, it’s not acceptable,” he stated after the match.
“This has been going on for a while and if you don’t stop this it will become a habit so I’ve told them [about it]. They know it themselves; they are a bunch of experienced players. We can score but we can also concede so we need to really work on that.”
Butler joined Tampines Rovers in June in his first foray into the football scene outside of New Zealand, where he has held the fort with Waitakere United since his youth days. Most recently he was a key member of the squad during the Group Stage of the 2014 OFC Champions League in Fiji.
At the time, the 29-year-old said after holding off in the past, the time was right for him to venture out and explore opportunities.
“My club back home was really good to me and I was loyal to them but when this opportunity came about I was keen to explore it,” Butler said.
“Tampines was looking for a player like me, a midfielder, and I think I fit the bill quite nicely. Now’s the right time for me to move on and I’m looking forward to playing good football.
“Pressure is something I’m used to, to be honest. I’ve been the captain of my team back home for five years and we’ve won the title four years in a row. We’re always under pressure to win. To me, any pressure is good pressure.”
Butler and his Tampines Rovers side next take on Police Sports Association on 19 July at Clementi Stadium in another League Cup match, before they return to the S-League at the end of the month.